FirebaseFirestore.instance
.collection(
'chats/${site}/conversations/${room.id}/messages')
.orderBy('createdAt', descending: true)
.where("createdAt", isGreaterThan: dateTime )
.snapshots()
.map(
(snapshot) {
So, On the first document that inserted to the firestore, the I get i a snapshot. On the second, the stream return the first and the second,
So the i get -
(Doc A)
(Doc A,Doc B)
(Doc A, Doc B, Doc C)
And so on. Is there a way to get:
(Doc A)
(Doc B)
(Doc C)
?
I reviewed your snippet and it appears you are using a Stream from the snapshot() method of a CollectionReference type. According to the documentation, this will stream events as they happen in Firestore. You mentioned that with each document inserted in Firestore, you also started getting the previous documents that were inserted before, instead of getting only the one which was just inserted (the latest). This might be related to the dateTime variable you are using to filter documents. Since you are using a greater than comparison, any documents created after the time set in the dateTime will be returned from the query. This could explain why your query returns additional documents each time a new one is added with a timestamp after the dateTime variable.
If you would like to get only the latest document added to the database each time, you can make use of a query limiter. I tested the limitToLast method to get only the latest document added and it appears to work in my testing. This method returns the very last document in a query, and in order for this to be the newest you would have to invert the process to order by ascending (oldest first) so that the newest document is at the bottom:
FirebaseFirestore firebase = FirebaseFirestore.instance;
firebase
.collection('users')
.orderBy('createdAt', descending: false) // orders by ascending order, latest document is the last
.limitToLast(1) // gets the last document, you can set how many docs to get
.get()
.then((QuerySnapshot snapshot) {
if (snapshot != null) {
// Data is available
snapshot.docs.forEach((doc) {
print(doc['firstName']);
});
} else {
print("No data found");
}
}
for everyone who reach this issue on 2022, the solution is rather simple.
You can stay with the same query but check the doc changes:
snapshot.docChanges.forEach((docChange) {
final data = docChange.doc.data() as Map;
LimitToLast won't solve your problem if the internet connection was down for a few moments and multiple updates arrived, but docChanges is all the changes since the last snapshot.
Note: You need to ignore the first time because it will return all the docs on the collection at the first time.
Related
Does QuerySnapshot only return added/updated/removed documents or all documents, not only updated ones, from Firestore?
If it returns all the documents, then is there any way to get only newly added/updated/removed documents?
What is the difference between getDocuments() and getDocumentChanges() in Firestore's QuerySnapshot and when to use them?
In the below code, is it returning all documents or only added/modified/removed documents? Because It's like we are getting all documents and then sorting them according to their state. Is it correct?
.addSnapshotListener { snapshots, e ->
if (e != null) {
Log.w(TAG, "listen:error", e)
return#addSnapshotListener
}
for (dc in snapshots!!.documentChanges) {
when (dc.type) {
DocumentChange.Type.ADDED -> Log.d(TAG, "New city:${dc.document.data}")
DocumentChange.Type.MODIFIED -> Log.d(TAG, "Modified city: ${dc.document.data}")
DocumentChange.Type.REMOVED -> Log.d(TAG, "Removed city: ${dc.document.data}")
}
}
}
Edit:
Here is my code
.addSnapshotListener { value, error ->
if (error != null) {
cancel(
message = "Error fetching posts",
cause = error
)
return#addSnapshotListener
}
if (value != null) {
Log.d(TAG, "main value: ${value.size()}")
for (dc in value.documents) {
Log.d(TAG, "dc ${dc.data}")
}
offer(reaction)
}
}
Initially, when the app is open I am getting all documents and it's ok. But when I am modifying one document still I am getting all documents(Log.d(TAG, "main value: ${value.size()}")answer is 2. I have a total of 2 documents right now so I am getting both documents modified and not modified). Means first I will get All documents and then I will sort them by using getDocumentChanges().
My code is in Kotlin.
Does QuerySnapshot only return added/updated/removed documents or all documents(not only updated ones) from Firestore?
A QuerySnapshot object contains all the results of a Firestore query. So if you perform a query in Firestore, all the results that are returned can be found in the QuerySnapshot object.
If it returns all the documents then is there any way to get only newly added/updated/removed documents?
Yes, there is. You use an addSnapshotListener(EventListener listener) to listen for updates in real-time. This means that can always view changes between snapshots. So you can be notified if a document is only added, modified, or removed. But please also note, that there is no way you can skip the initial retrieval of the documents.
What is the difference between getDocuments() and getDocumentChanges() in Firestore's QuerySnapshot and when to use them?
The getDocuments() method:
Returns the documents in this QuerySnapshot as a List in order of the query.
While getDocumentChanges() method:
Returns the list of documents that changed since the last snapshot.
So each method does a different operation.
Edit:
In the below code, is it returning all documents or only added/modified/removed documents? Because It's like we are getting all documents and then sorting them according to their state. Is it correct?
It will get all documents when you are first opening the app, and unfortunately, this behavior cannot be changed. Right after that, each method will fire according to the performed operation. For example, if a document is added, you'll only get a single document in the ${dc.document.data}.
I'm building a Self-learning app with differente questions types. Right now, one of the questions have a field containing a list of DocumentReferences:
In Flutter, I have the following code:
Query<Map<String, dynamic>> questionsRef = firestore
.collection('questions')
.where('lesson_id', isEqualTo: lessonId);
await questionsRef.get().then((snapshot) {
snapshot.docs.forEach((document) {
var questionTemp;
switch (document.data()['question_type']) {
....
case 'cards':
questionTemp = CardsQuestionModel.fromJson(document.data());
break;
....
}
questionTemp.id = document.id;
questions.add(questionTemp);
});
});
Now, with "questionTemp" I can access all the fields (lesson_id,options,question_type, etc..), but when it comes to the "cards" field, how Can I access the data from that document reference?
Is there a way to tell firestore.instance to get the data from those references automatically? Or do I need to make a new call for each one? and, if so, how can I do that?
Thank you for your support in advance!
Is there a way to tell firestore.instance to get the data from those
references automatically? Or do I need to make a new call for each
one?
No there isn't any way to get these documents automatically. You need to build, for each array element, the corresponding DocumentReference and fetch the document.
To build the reference, use the doc() method
DocumentReference docRef = FirebaseFirestore.instance.doc("cards/WzU...");
and then use the get() method on this DocumentReference.
docRef
.get()
.then((DocumentSnapshot documentSnapshot) {
if (documentSnapshot.exists) {
print('Document exists on the database');
}
});
Concretely, you can loop over the cards Array and pass all the Futures returned by the get() method to the wait() method which "waits for multiple futures to complete and collects their results". See this SO answer for more details and also note that "the value of the returned future will be a list of all the values that were produced in the order that the futures are provided by iterating futures."
How I can order data doc by two field, My app have a stream builder and I want order the data by the time that wrote and if the todo important so there is two field in docs one for time and there is boolen value
i want the data order by the time and if the data important that is mean the boolen true to be in the top of the list of stream and when i add data will show ender it. this the code I used for strem
final FirebaseFirestore firestore;
DataBase({this.firestore});
Stream streamTodos({String uid}) {
try {
return firestore
.collection("homeNeeds")
.doc(uid)
.collection('homeNeeds')
.orderBy('time', descending: true)
.snapshots();
} catch (e) {
return e;
}
}
// i tried to put tow orderBy('time', descending: true).orderBy('pin', descending: true)
and it doesn't work the snap shot return empty
it appears that is not as simple as saying you can or you can not, it depends on your specific case, but most likely you'll have to do it client-side.
There is another question like this one here:
You can use multi_sort: ^3.0.0 in this case.
https://pub.dev/packages/multi_sort
I solved this problem by adding Indexes in cloud firestore and that option allow you to use tow orderby in the same code
hi i am trying to increment a value when clicked the button if data is available in firestore this is my code bloc if you have any suggestion lmk please
int q = 0;
final snapShot = await Firestore.instance.collection('cart').document("LIihBLtbfuJ8Dy640DPd").get();
if(snapShot.exists){
q=q+1;
}
Firestore.instance.runTransaction((Transaction transaction) async {
await transaction.update(
Firestore.instance
.collection("cart")
.document("LIihBLtbfuJ8Dy640DPd"),
{
foodItem.name: {
'itemName': foodItem.name,
'imgUrl': foodItem.imageAssetPath,
'itemPrice': foodItem.price,
'quantity': q,
}
});
});
In November 2021, this worked for me.
FirebaseFirestore.instance.collection('users').doc(currentUser?.id).update({
'bronzeBadges': FieldValue.increment(2),
});
var quantityref = db.collection("cart").document("LIihBLtbfuJ8Dy640DPd");
// Increment the quantity field by 1.
quantityref.update({
"quantity" : firebase.firestore.FieldValue.increment(1)});
If your want to change a value based on the previous one, you have basically two approaches:
Make use of transactions. I see you're doing that but incorrectly, because you're fetching the current value outside of it, and it could change by the moment you run the update, causing data inconsistencies. I don't know about Flutter, but as far as I know, a Transaction in Firebase consists in a read operation followed by one or more write operations, and the value returned from the read will be the very last one and won't be changed before you finish the transaction, so you can be sure you're working with the latest one. I suggest you to read the Transactions docs.
increment method (recommended): See this see this answer for incrementing in Flutter
First of all, you need to get the desired document and its elements to update the document of fields. In your example, it is quantity.
First, get the document:
Firestore.instance
.collection('cart')
.document('documentID')
.get()
.then((DocumentSnapshot ds) {
// use ds, parse ds then access the quantity
});
After doing the job, you need to update the field. Thankfully, there is an updateData function in firestore instance.
db.collection('cart')
.document('documentID')
.updateData({'quantity': someQuantity});
Hope it helps.
I get some data from firestore. Sometimes when I called to get data, the collection is not created yet.
before calling get request, how do I check collection is exists or not?
Stream<List<ChatModel>> getChat(ChatFieldModel model) {
var ref = _db.collection('chats');
return ref
.document(model.docId)
.collection('messages')
.orderBy('timestamp', descending: true)
.snapshots()
.map((list) =>
list.documents.map((doc)=>ChatModel.fromForestore(doc)).toList());
}
I posted this before
final snapshot = await firestore.collection(roomName).getDocuments();
if (snapshot.documents.length == 0) {
//doesnt exist
}
Hope this helps
Collections are not created or deleted independently of documents. When you create a document and specify it as being part of a certain collection, that collection is created automatically if it does not already exist. Similarly, when you remove the last document in a collection, that collection will automatically be deleted. So there is really no circumstance where you need to worry about whether a collection has been created or not, and you have no explicit control over creating or deleting collections.
Usually a collection in Firestore gets deleted if no Documents exist in it.
However, there might be cases where you want to keep a history of the collection modification events, or let's say for some reason prevent Collections from being deleted.
Or for example, you want to know when a collection was created in the first place. Normally, if the Documents are deleted, and then the Collection gets created again, you will not know the initial creation date.
A workaround I can think of is the following:
Initialize each collection you want with a Document that will be specifically for keeping generic info about that collection.
For example:
This way, even if all other Documents in the Collection are deleted, you'll still keep the Collection in addition to some info that might be handy if In the future you need to get some history info about the Collection.
So to know if a Collection exists of no, you can run a query that checks for a field in Info Documents (eg CollectionInfo.exists) to know which Collections have been already created.
This is for the most recent update
final snapshot = await FirebaseFirestore.instance
.collection('collection name').get();
if ( snapshot.size == 0 ) {
print('it does not exist');
}
Feb 2022
Get QuerySnapshot and return querySnapshot.docs.isNotEmpty or isEmpty
Future<bool> isItems() async {
CollectionReference collectionReference =
_firestore.collection("users").doc(_user!.uid).collection("cart");
QuerySnapshot querySnapshot = await collectionReference.get();
return querySnapshot.docs.isNotEmpty;
}
await FirebaseFirestore.instance
.collection('collectionName')
.limit(1)
.get()
.then((snapshot) {
if (snapshot.size == 0) {
print("No collection");
}
});